1. Field of the Invention
The present invention relates to an endoscope insertion portion of an endoscope having a plurality of observation optical systems.
2. Description of the Related Art
Conventionally, endoscopes have been widely used in the medical field and the like. With an endoscope, for example, internal organs in a body cavity can be observed by inserting an elongated insertion portion into the body cavity, and various treatments can be performed using a treatment instrument inserted into a treatment instrument insertion channel as necessary. At a distal end of the insertion portion, a bending portion is provided. By operating an operation portion of the endoscope, observing direction of an observation window at a distal end portion can be changed.
In general, an endoscope is provided with an air/water feeding nozzle for cleaning for a case where body fluid or the like adheres on an outer surface of the objective optical system of the endoscope to disturb the observation when the endoscope is inserted into the body cavity. The outer surface of the objective optical system of the endoscope can be secured of a clean observation field of view with, for example, a cleaning liquid spouted out or air sprayed from the air/water feeding nozzle.
For example, an endoscope having a plurality of objective optical systems is proposed as described in Japanese unexamined patent publication No. 06-154155. This endoscope has a plurality of image pickup units, wherein the plurality of objective optical systems and an aperture of an air/water feeding nozzle are located at a distal end of an insertion portion to line up on a generally straight line.
Endoscopes used in recent years have a duct used for inserting various forceps and sucking body fluid, filth or the like in the body cavity (hereinafter referred to as treatment instrument channel), and a duct used for spraying a cleaning liquid in a direction of a diseased part to clean mucous membranes or the like adhering on a diseased part as a region to be inspected (hereinafter referred to as forward water-feeding channel). Respective aperture portions of the treatment instrument channel and the forward water-feeding channel are disposed on a distal end surface of a distal end portion.
Japanese unexamined patent publication No. 03-165731, for example, discloses an endoscope disposed with only one image pickup unit, in which a convex portion is provided between a lens and a nozzle. Further, Japanese Patent Laid-Open No. 2003-210388, for example, discloses an endoscope including a distal end cover having a distal end surface with a flat portion, an observation window protruding to a predetermined height from the flat portion, a gradient portion formed between a distal end surface periphery of the observation window and the flat portion, and illumination windows protruding from the flat portion to the same predetermined height as the observation window and provided to oppose to each other over the observation window.